Temporal structure of cone inputs to cortical color cells
The color of a stimulus can be made more salient if it is immediately preceded by a stimulus of opposite color, a phenomenon known as successive or temporal color contrast (Helmholtz, 1909, pg. 243; Figure 3.1). Here I tested whether color cells in monkey V-1 could mediate this temporal chromatic contrast. I did this using sequential colored stimuli (consisting of small patches of cone isolating light) presented to the centers of V-1 cell receptive fields. All colored stimuli were brighter than the constant adapting background on which they were presented. For almost all color cells (33/35), the response to a stimulus was reduced if the stimulus was immediately preceded by a similarly colored stimulus. But the response was increased if the stimulus was preceded by an oppositely colored stimulus. I tested 12 non-color cells in a similar way; for all of these cells, I found that a previous stimulus, regardless of its color, reduced the response to a subsequent one. Thus color cells are specifically capable of encoding temporal color contrast. Many color cells were also Double-Opponent, a receptive field organization that makes them well suited to code spatial color contrast. Thus these cells seem well equipped to mediate two key features of color vision: simultaneous and successive color contrast.
KeywordsReceptive Field Color Cell Color Contrast Colored Stimulus Stimulus Range
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